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timing advance

Cheng

New member
what device adjusts the advanced timing on a delco ignition electronic ignition system. the port engine has only a few degrees difference from idle time and high speed time. Its on a 350 crusader 1990 model
 
Thanks for the prompt reply, I'll try to describe the distributor, it has a large square opening that accepts 2 plug in connections, inside of course the rotor, below that a metal ring that semi rotates about a quarter inch each way on the outside of the 8 point rotating element, below that, is a coil pick up that is clipped into the ignition control module which is connected to the mentioned 2 plug in connections. My timing plate on the timing chain has rusted with no reference marks, the initial timing I believe is 10 deg BTDC. Is there a 0 degree reference point on that indicator plate. The plate consists of a number of v notched marks, in the 2 o'clock area on the timing chain cover. the v notches going from the top of the plate have small v's with one large V app. a couple of notches from the lower end of the plate. vvvvvvVvv. As mentioned in the first thread the advance only moves app. 1/4' total when engine is rev'ed
 
Likely you have the DELCO EST system (aka Voyager)...the advance curve is controlled by the module and is not adjustable. the module has two connectors: the two pin connector goes to the coil and the four pin connector goes back into the wiring harness.

It is best to set them so the max advance is correct and live with the initial timing...

the timing tab will have numbers "inside" the V's..you might try wire brushing it or just get a new one...they are different on counter rotating engines.
 
Likely you have the DELCO EST system (aka Voyager)...the advance curve is controlled by the module and is not adjustable. the module has two connectors: the two pin connector goes to the coil and the four pin connector goes back into the wiring harness.

It is best to set them so the max advance is correct and live with the initial timing...

the timing tab will have numbers "inside" the V's..you might try wire brushing it or just get a new one...they are different on counter rotating engines.

So I understand set the timing to max advanced (total advanced timing) via the distributer, which will place it off the timing tab? This engine will fire at 25 degrees BTDC at all times if so. What can I replace to get the curve back in. !0Deg BTDC at idle and have it advance to 25 at throttle up ?
 
if the timing is NOT being advanced by the module, as the engine's RPM increases, then you need to replace the module first.

Once the timing is advancing ok, then I'd suggest setting the timing, at max advance, to the specified value. You then live with the timing provided by the module at all lower RPMs.

How you set the timing is driven by the equipment you use...some prefer the basic timing light, some prefer the newer "advance" style.
 
if the timing is NOT being advanced by the module, as the engine's RPM increases, then you need to replace the module first.

Once the timing is advancing ok, then I'd suggest setting the timing, at max advance, to the specified value. You then live with the timing provided by the module at all lower RPMs.

How you set the timing is driven by the equipment you use...some prefer the basic timing light, some prefer the newer "advance" style.

Stupid ? time if base time is 8 deg BTDC, advance total time is 25Deg BTDC?, or 17 deg ATDC. I'm trying to understand which way the line on the harmonic balance moves on the clockwise and counter clockwise rotating engines. In my understanding advance goes towards TDC, Retard goes away from TDC?
 
Best thing to do is use a "regular" timing light and the pointer's ZERO mark in conjunction with a "timing tape"...and alternative is to use an "advance" timing light. an alternative is to mark the balancer after a careful measurement. the standard timing tap doesn't go to 30 degrees so us need an alternative approach as described above.

Timing "advances" as the engine rpm increases because it take a finite amount of time for the air/fuel charge to burn...so advancing the timing means the spark occurs even further before top dead center.

when you apply a timing tape or just scribe lines, remember that the BTDC marks will come under the timing tap and then "count down" towards zero (TDC)...so, as the balancer spins, 40 deg BTDC comes under the tab, then 30 deg BTDC, etc and the orientation will reverse on the opposite rotation engine...
 
Timing "advances" as the engine rpm increases because it take a finite amount of time for the air/fuel charge to burn...so advancing the timing means the spark occurs even further before top dead center.

I think that this statement is key to understanding that the term advance can be seen more as increasing the amount of negative timing (timing retard), so at 750 rpm the spark occurs at about 8 degrees before the piston is at top dead center, and that at about 3000 rpm the spark occurs much earlier perhaps at 25-30 degrees before TDC.
 
i wouldn't consider it "negative timing" or timing retard....Think of the piston heading to TDC on the compression stroke...if the time it takes the charge to burn is fixed, say at idle, you will have to start the process much earlier (on terms of crankshaft degrees) when the engine is spinning at 3000 rpm
 
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